Method of increasing viscosity of an aqueous solution with a sulfo betaine polymer

ABSTRACT

The present invention relates to homopolymers and copolymers of N-(4-sulfoalkyl)N-methyldiallyl ammonium betaines which are useful as aqueous viscosification agents.

This is a division of application Ser. No. 822,841, filed 1-27-86, nowU.S. Pat. No. 4,708,998.

BACKGROUND OF THE INVENTION

The betaines are a special class of zwitterions. These materials areself neutralized and contain no counterions. Moreover, the positive andnegative charges are separated by alkyl groups.

Saturated nonpolymerizable betaines are well known in the detergent andfiber fields. Both carbonyl and sulfo-saturated betaine compounds areclaimed in such patents as U.S. Pat. Nos. 3,649,677; 4,088,612;3,539,521; and 4,381,980.

Polymerizable monounsaturated carboxy betaine monomers, e.g.,carboxymethacrylate betaine monomers (I) and polymers (II) arewell-known and disclosed in U.S. Pat. No. 2,777,872 (Jan. 15, 1957),U.S. Pat. No. 2,834,758 (May 13, 1958) and U.S. Pat. No. 2,846,417 (Aug.5, 1958). ##STR1##

Carboxyvinylpyridine betaine monomers and homopolymers (II) have alsobeen reported [H. Ladenheim and H. Morawetz, J. Poly. Sci. 26, 251(1957)]. ##STR2##

Polymerizable monounsaturates sulfoalkyl betaine monomers such as:##STR3## are taught in such patents as U.S. Pat. Nos. 3,547,985,3,473,998, 3,484,479 and Ger. Auslegeschrift No. 1,207,630, and in sucharticles as Hart and Timmerman, J. Olym. Sci. 28 118 (1958) and GalinPolymer 25 121,254.

Cyclopolymerizable alkyl quaternary ammonium salts, e.g., ##STR4##wherein R' and R" are alkyl groups, are described in the article byButler [J. Am. Chem. Soc. 79 3128 (1957)].

Cyclopolymerizable N-carbomethoxymethyl-N-alkyl-N-N-diallyl ammoniumchloride, ##STR5## is described in Eur. Pat. EP 55,048 (June 30, 1982).The above monomer cyclopolymerizes to form polymers of the type,##STR6## These polymers in turn, can be hydrolyzed to form cyclo carboxybetaine polymers ##STR7## where are useful as antimicrobial polymers.

N-Na carboxylate-N-methyl-N-N-dialkyl ammonium betaine monomer isdisclosed in U.S. Pat. No. 3,935,495 by the reaction ofN-methyl-N-N-diallylamine with the sodium salt of bromoacetic acid.However, the preparation of this monomer requires mixed solvents andseveral steps (i.e., preneutralization of the bromoacid reaction withthe tertiary amine and extraction with benzene) and mixed solvents (H₂O/acetone.)

SUMMARY OF THE INVENTION

The instant invention describes a novel cyclopolymerizableN-(4-sulfoalkyl) N-methyldiallyl amine ammonium betaine monomer,##STR8## wherein R' is an alkyl group of 1-20 carbon atoms and whereinR" is an alkyl group having about 3 to about 4 carbon atoms.

The instant monomer differs from the saturated nonpolymerizable betaineart because the instant monomer is homo- and copolymerizable. Theinstant monomer differs from the other monounsaturated betaine monomersbecause it is diunsaturated and forms rings on polymerization. It alsohas no hydrolyzable weak links, like amides or esters.

The instant invention is distinct from Butler's diallylcyclopolymerizable quaternary ammonium salts because the instantdiallylic monomer is dipolar or zwitterionic and is less salt andpH-sensitive than the Butler compounds.

The present invention also differs from the cyclopolymerizableN-carbomethoxymethyl-N-N-diallyl ammonium chloride of Eur. Pat. EP55,048 (June 30, 1982) because the present invention copolymerizesdirectly to a betaine cyclopolymer without the need of an esterintermediate. Also, the instant invention leads to cyclic sulfobetainesand not cyclic carboxybetaines; it is generally known that sulfonatedproducts are more stable than carboxylated products.

The instant invention is superior to that of U.S. Pat. No. 2,935,493both in product and process. The present product is a sulfobetaine whichis expected to show improved stability, and it is prepared in a one-stepprocess in a single solvent.

The present invention also relates to unique and novel betaine,homopolymers and copolymers of N-(4-sulfoalkyl) N-methyldiallylamineammonium betaine (MDABS). Such materials contain both positive andnegative charges.

The present homo- and copolymers are distinguished from thecarboxymethacrylate betaine homopolymers and copolymers (U.S. Pat. Nos.2,777,872, 2,834,758, 2,846,417) because sulfonate vs. carboxylateanions and low vs. high charge densities are used. Furthermore,carboxylate anions are limited by their known susceptibility toprecipitation by polyvalent cations (e.g., Ca⁺⁺); the latter species areoften found in geological formations [F. J. Glaris in "Water SolubleResins" 2nd Ed., R. L. Davidson and M. Sittig, Eds. Rheinhold, NY, p.168]. Sulfonate anions are not so limited.

The present invention is distinguished from the previous sulfobetainehomo- and copolymers in the following ways: different structures, andhigher thermal stabilities as measured by T₆ A.

GENERAL DESCRIPTION OF THE INVENTION

The present invention relates to a method for increasing the viscosityof an aqueous solution which comprises the step of dissolving about 0.1to about 5.0 wt% of a water soluble betaine homopolymer-copolymer in theaqueous solution, wherein the aqueous solution is selected from thegroup consisting of water, a brine solution, an acid solution or a basesolution, wherein the concentration of the salt, acid or brine in theaqueous solution is about 0.01 to about 5.0 wt%.

The viscosifying agents for aqueous and saline solutions of the presentinvention are betaine copolymers formed by a homogeneous, free radical,copolymerization, wherein the N(4-sulfoalkyl) N-methyldiallyl amineammonium betaine monomer is polymerized with itself or copolymerizedwith acrylamide or N-vinylpyrrolidone monomer, wherein the mole percentof the betaine unit is about 1 to about 99 mole percent, more preferably20 to 80, and most preferably 30 to 70.

The N-(4-sulfobutyl) N-methyldiallyl amine ammonium betaine monomer hasthe formula: ##STR9## wherein R' is an alkyl group of about 1 to about20 carbon atoms and R" is an alkyl group having about 3 to about 4carbon atoms.

The viscosities of aqueous solutions of these homopolymers andcopolymers were measured by means of a Contraves™ low shear viscometermodel LS30 using a No. 1 cup and No. 1 bob. Temperatures were controlledto ±1° C., and measurements were made at a rotational speed that gave ashear rate of 1.28 s⁻¹.

The homogeneous polymerization process of the instant inventioncomprises the steps of forming a mixture of betaine monomer andoptionally a comonomer and either water or a brine solution to form areaction solution; heating said reaction solution to at least 50° C.;adding a free radical initiator to said reaction solution to initiatethe homopolymerization or copolymerization of the comonomer and theN-(4-sulfobutyl)N-methyldiallylmine ammonium betaine monomer;polymerizing the monomers at a sufficient temperature and for asufficient time to form the water soluble homopolymer or copolymer ofN-C4-sulfobutyl/N-methyldiallyl ammonium betaine monomer; and recoveringthe water soluble homo- or copolymer from the reaction solution. Thespecific details of polymerization are set forth in the Examples herein.

Suitable free radical initiators for the instant freeradical-copolymerization process are potassium or ammonium persulfate;sodium thiosulfate, potassium persulfate mixture; benzoyl peroxide, AIBNand modified AIBN and other common free radical initiators. Theconcentration of the free radical initiator is about 0.02 to about 0.50grams per 100 grams of total monomer.

Polymerization of the acrylamide monomer or N-vinylpyrrolidone andN-(4-sulfobutyl)N-methyldiallyl ammonium betaine monomer, orhomopolymerization of the betaine monomer is effective at a temperatureof about 25° to about 90° C., more preferably at about 30° to about 65°C., and most preferably at about 45° to about 55° C. for a period ofabout 1 to about 48 hours, more preferably at about 2 to about 36, andmost preferably at about 4 to about 24. A suitable method for recoveryof the formed copolymer from the reaction solution comprisesprecipitation by means of a non-solvent, such as acetone.

The N-(4-sulfobutyl)N-methyldiallyl ammonium betaine monomer is preparedby forming an acetone solution under a nitrogen blanket ofN-methyldiallamine and butane sulfate and heating the solution withstirring to 50° C. for about 48 hours. The reaction solution is cooledto 25° C. and the precipitate of the N-(4-sulfobutyl)N-methyldiallylbetaine monomer is recovered by filtration. The4-(4-sulfobutyl)N-methyldiallyl ammonium betaine monomer can bepolymerized by subjecting the monomer to a free radical initiator suchas potassium persulfate at about 50° C. for about 23 hours under anitrogen blanket to form the polymer, polyN-(4-sulfobutyl)N-methyldiallyl ammonium betaine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following examples illustrate the present invention without,however, limiting the same hereto.

EXAMPLE 1 Prep N-(4-Sulfobutyl) N-Methyldiallylamine ammonium betaine(MDABS)

The sulfobutylation of N-methyldiallylamine was carried out in a allglass reaction vessel equipped with a water cooled condenser,thermometer, stirrer, addition funnel and nitrogen inlet.

A solution of 1 mole of freshly distilled N-methyldiallylamine (VirginiaChemicals) in acetone was added to the reaction vessel. While the batchwas stirring a solution of distilled butaine sultone (Aldrich) inacetone was added until solution was homogeneous, then the solution washeated to 50° C. with stirring under nitrogen for 48 hr. The reactionwas cooled to 25° C. and the M-DABS monomer was recovered as aprecipitate by filtration. The precipitate was washed thoroughly withacetone and vacuum dried at 25° C. The MDABS monomer was purified byrecrystallization from isopropanol.

Initial yield 35%

M.P. 115° C.

Final 30% (after recry).

The product showed ionic sulfonate bands in the IR at 1180-1210 cm⁻¹ and1040 cm⁻¹, as well as nonconjugated olefin (--C═C--) at 1645 cm⁻¹.

Theoretical elemental analysis: C=53.42%; H=8.56%, N=5.66; S=12.96

Found elemental analysis: C--53.03%; H=8.67%; N=5.32; S=13.16

Yields between 80-90% are possible using toluene as solvent and at ahigher reaction temperature.

EXAMPLE 2 Prep. Poly(N-(4-sulfobutyl)N-methyldiallylamine AmmoniumBetaine) Poly (MDABS)

A 100 ml all glass reaction vessel was equipped with a magnetic stirbar, thermometer, nitrogen inlet and water cooled condenser. Add 40 gdist. water and deoxygenate by heating at 50° C. for 1 hr. whilestirring with a rapid nitrogen purge. A 10 g quantity MDABS monomer wasdissolved and a 1 g quantity (44%) potassium persulfate soln. stirredand heated was added. The batch was under a nitrogen blanket for 23 hrs.Afterward the batch was cooled to 25° C. and precipitated into hotisopropanol, isolated by filtration and vacuum dried at 30° C. Thepolymer is crystalline and has a Tm=142° C. by DSC. The thermalstability of this homopolymer as measured by the onset of major weightloss by TGA(N₂) was 370°=25° C. This is considerably higher than thedecomposition temperatures of other polybetaines, such as poly[N-(3sulfopropyl)N-methacroyloxyethyl-N₉ N-dimethyl-ammonium betaine,328°±25° C., and the betaine homopolymer of 2 vinyl pyridine, 305°±25°C.

EXAMPLE 3 Prep. Poly(Acrylamide-co-N-(4-Sulfobutyl)N-methyl DiallylamineAmmonium Betaine) Poly(Am co MDABS)

A 1 liter all glass reaction vessel was equipped with an air driven stirmotor, stirrod, thermometer, nitrogen inlet and water cooled condenser.A 365 g quantity of distilled water was added and deoxygenated byheating for 1 hr. at 50° C. while stirring with a rapid nitrogen purge.A 23.5 g quantity of acrylamide+2.1 g MDABS monomer was dissolved and a1 g quantity (0.90%) potassium persulfate soln. was added. The batch wasstirred and heated under a nitrogen blanket for 18.5 hr., cooled to 25°C., precipitated into methanol, isolated by filtration, and vacuum driedat 30° C. The product was found to contain 0.90 mole% betaine byelemental analysis (uncorrected for water) and had a Tg of 92° C. byDSC.

EXAMPLES 4 and 5 (12P, 13P) Additional Copolymerization of MDABS with AM

The method of Example 3 was repeated except that comonomer charge wasvalued according to Table 1.

                  TABLE 1                                                         ______________________________________                                               Mole %   Mole %                                                               MDABS    MDABS       Brookfield                                                                              [η]                                 Example                                                                              Charged  Incorporated                                                                              1.5% Dist. H.sub.2 O                                                                    2% NaCl                                 ______________________________________                                        4 (12P)                                                                               5.0     1.80        850 cp    6.4 dl/g                                5 (13P)                                                                              10.0     3.26        275 cp    5.4 dl/g                                ______________________________________                                    

EXAMPLE 6 Coppolymerization of M-DAPS with AM

The method of Example 4 was repeated except that the N-(3sulfopropyl)N-methyldiallylamine (M-DAPS) was substituted for N-(4sulfobutyl)N-methyldiallylamine ammonium betaine (M-DABS).

Brk. vis. (1.5% in H₂ O) 75 cp

EXAMPLE 7 Preparation of Copolymer of MDABS with NVP

A 20.0 g (0.08 mol) quantity of MDABS and a 8.98 g (0.08 mol) quantityof NVP were dissolved in 150 ml H₂ O and polymerized with 0.035 g(1.29+10^(-r) mol) of an azo initiator (V-50) at 60° C. for one week.After this time, 100% yield of product was isolated.

What is claimed is:
 1. A method for increasing the viscosity of an aqueous solution which comprises the step of dissolving in said aqueous solution a water soluble polymer selected from the group consisting of N-(4-sulfoalkyl)N-methyl diallyl ammonium betaine and N-vinyl-pyrrolidone, N-(4-sulfoalkyl)N-methyl diallyl ammonium betaine and acrylamide and poly-N-(4-sulfoalkyl)N-methyldiallyl amine ammonium betaine. 